How is it determined?

[JohnH]

Fella comes up with a new case, How is an appropriate powder decided on??? An why is it that in some cases, straightwalls particularly, that powders which are a tad slower than the normally accepted speeds seem to give higher velocities than they might seem to just looking at a burn chart. 2495 comes to mind in the 38-55 and R15 as well as 4064 comes to mind in the 30-30

[buck1]

Fella comes up with a new case, How is an appropriate powder decided on??? An why is it that in some cases, straightwalls particularly, that powders which are a tad slower than the normally accepted speeds seem to give higher velocities than they might seem to just looking at a burn chart. 2495 comes to mind in the 38-55 and R15 as well as 4064 comes to mind in the 30-30


I look up the highest speed with the lowest pressure, to find my starting powder.
I think the lower pressure spike and longer bbl time helps with the boolit speed.....Buck